Why does a deep sea diver carry oxygen cylinder on his/her back?

Why does a deep sea diver carry oxygen cylinder on her back?

What do the mountaineers and deep sea divers carry on their backs ?

Helium - oxygen mixture is used be deep sea divers in preference to nitrogen - oxygen mixture because

Here is a news strip, read it carefully and answer the following questions Villagers oppose sand mining project Santhabommali (Srikakulam): People of more than 20 villages in two mandals of Srikakulamhave raised a banner of revolt against the proposed beach sand mining project by a private company and threatened to intensify their agitation if the government does not cancel the project. The sand mining is being taken up to extract rich minerals from the area. The villages are located around the forest belt were mining was initiated. Why does the private company want to carry out mining in the beach area?

Many great rivers flow towards the equator, what effect does the sediment they carry to sea have on the rotation of the earth?

(A) Deep sea divers use helium-oxygen mixture for respiration (R) Unlike nitrogen, helium is not soluble in blood even under high pressure.

Why does the amount of oxygen vary between exhaled and inhaled air ?